THE JURASSIC FLORA OF CAPE LISBUBNE, ALASKA. 43 



that of Cape Boheman and Siberia, appeai-s to liave nothino; in common with that of tho Ahis- 

 kan locahty. 



Tho hirge and interesting Ikira o*' the ishmd of Bornliohn, whicli was Ihst described by 

 Bartholin and later and more fullj^ by Moller',' was regarded l)y the latter as of Rhsetic or 

 Liassic age. It is, as Seward has pointed out, "no doubt younger than the Rhsetic floras of 

 Scania, Tonldn, and Franconia, and the number of Lower Oolite species which it includes 

 would seem to favor the view that its affinities are rather wdth Jurassic than with Rhaetic floras 

 of other regions." Tliis statement is, at least to some extent, borne out by the following 

 species from Cape Lisburne wluch ar(^ found also in Bornholm: Podozamites lanceolatus, Crinl'go 

 digitata, Phcenicopsis angustifolia, and PagiopJiyllnm hurrii. 



Turnmg now to the rich and wi'll-exploited Jurassic floras of England, we find Cmiiopteris 

 TtymenophyUoides, G-inl-go digitata, and Zamites megapliyUus, of the Great Oolite (Bathonlan), 

 in common with the Alaskan flora here discussed. Similar beds in Sutherland carry Coniopteris 

 hymenopliyTlokles, Ginl-go digitata, and Elatides cunnfolin. 



The rich Jm-assic flora from Douglas County, Oreg., as worked up by Fontaine,- mcludcs 

 the following species which appear to be present also m the Cape Lisburne region, though not 

 all are listed here under the same names: Coniopteris Tiymenophylloides, Tliyrnoptiris inurrayana, 

 Cladopllehis vaccensis, Podozamitis lanciolatus, P. I. latijolius, P. pulcJuUuN, Oinlgo digitata, 

 and Phcenicopsis sp. 



From the composition and wide distribution of tliis flora as outlined above, the fhial 

 conclusion is reached that the Corwin formation of the Cape Lisburne region is undoubtedly 

 Jurassic in age, belonging either in the upper part of the Middle Jm^assic or Brown Jura, or 

 the extreme lower portion of the Upper Jurassic or White Jura — that is to say, it is probably 

 not older than the Bathonian and certainly not younger than the Oxfoidian. 



DISTRIBUTION OF JURASSIC FLORAS. 



GEOGRAPHIC RANGE. 



At lliis point it may be of general interest briefly to rcA-iew the character and geograpliic 

 range of Jurassic floras, especially as developed in Ai'ctic and Antarctic regions. The wide 

 area! distribution of Middle and Upper Jurassic floras has long been one of the mai'vels of 

 plant distribution. The living flora, of course, affords many incU^adual examples of wide dis- 

 tribution, such as those found throughout the Tropics of both hemispheres, and others, chiefl}' 

 weeds, that have, largely through human agencies, spread widely over temperate lands, but 

 altogether these plants foim but an insignificant part of the whole flora, whereas in Jm-assic 

 time a large percentage of the whole flora was practically world-wide in its range. 



In Alaska well north of the Ai'ctic Circle is found the interestmg flora described in tliis 

 paper. Although only a few fossil species are at present known to occur at Cape Lisburne, 

 it is more than probable that the number would be greatly increased by careful examination, 

 but the region is difllcult of access and we must possibly await the exploitation of its coal 

 resources before adequate investigation of the flora will be made. 



The Jurassic flora has been found at a number of other localities in Alaska, the farthest 

 north being a point between Icy Cape and WainwTight Inlet, about 180 miles northeast of 

 Cape Lisburne. Another locality is near Nikolai, in the Copper River region, which has 

 afTordcfl a single species of Sag('no[)teris that is closely related to a form from the Lower Oolite 

 of Italy and has also been found in Oregon and California. Tins species came from a bed 

 now known as the Kennicott formation,' where it was found in association with marine inverte- 

 brates of T'ppcr Jurassic age. The largest representation of Jurassic plants in Alaska, aside 

 from that of Cape Lisburne, is found on the north shore of Cook Inlet, where seven or eight 

 species were obtained. These occur in the "Enochkin formation" of Stanton and Martin,* in 



' MOUer, Hjalmar, Kont;!. Sven.ska Vctenskaps-Akad. Hand!., vol. 36, No. 6, 1903. 



2 V. S. Geol. Survey Mon. 48, pp. 47-145, PLs. VI-XXXVIII, 1905. 



> U. S. Geol. Survey Hull. 448, pp. 31-43, 1911. 



< Oeol. Soc. America Hull., vol. 16, pp. .■897 et seq., 1905. 



19205°— 14 2 



